org.apache.commons.csv.Lexer Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.csv;
import static org.apache.commons.csv.Constants.BACKSPACE;
import static org.apache.commons.csv.Constants.CR;
import static org.apache.commons.csv.Constants.END_OF_STREAM;
import static org.apache.commons.csv.Constants.FF;
import static org.apache.commons.csv.Constants.LF;
import static org.apache.commons.csv.Constants.TAB;
import static org.apache.commons.csv.Constants.UNDEFINED;
import static org.apache.commons.csv.Token.Type.COMMENT;
import static org.apache.commons.csv.Token.Type.EOF;
import static org.apache.commons.csv.Token.Type.EORECORD;
import static org.apache.commons.csv.Token.Type.INVALID;
import static org.apache.commons.csv.Token.Type.TOKEN;
import java.io.Closeable;
import java.io.IOException;
/**
* Lexical analyzer.
*
* @version $Id: Lexer.java 1742468 2016-05-05 20:02:35Z britter $
*/
final class Lexer implements Closeable {
/**
* Constant char to use for disabling comments, escapes and encapsulation. The value -2 is used because it
* won't be confused with an EOF signal (-1), and because the Unicode value {@code FFFE} would be encoded as two
* chars (using surrogates) and thus there should never be a collision with a real text char.
*/
private static final char DISABLED = '\ufffe';
private final char delimiter;
private final char escape;
private final char quoteChar;
private final char commentStart;
private final boolean ignoreSurroundingSpaces;
private final boolean ignoreEmptyLines;
/** The input stream */
private final ExtendedBufferedReader reader;
Lexer(final CSVFormat format, final ExtendedBufferedReader reader) {
this.reader = reader;
this.delimiter = format.getDelimiter();
this.escape = mapNullToDisabled(format.getEscapeCharacter());
this.quoteChar = mapNullToDisabled(format.getQuoteCharacter());
this.commentStart = mapNullToDisabled(format.getCommentMarker());
this.ignoreSurroundingSpaces = format.getIgnoreSurroundingSpaces();
this.ignoreEmptyLines = format.getIgnoreEmptyLines();
}
/**
* Returns the next token.
*
* A token corresponds to a term, a record change or an end-of-file indicator.
*
*
* @param token
* an existing Token object to reuse. The caller is responsible to initialize the Token.
* @return the next token found
* @throws java.io.IOException
* on stream access error
*/
Token nextToken(final Token token) throws IOException {
// get the last read char (required for empty line detection)
int lastChar = reader.getLastChar();
// read the next char and set eol
int c = reader.read();
/*
* Note: The following call will swallow LF if c == CR. But we don't need to know if the last char was CR or LF
* - they are equivalent here.
*/
boolean eol = readEndOfLine(c);
// empty line detection: eol AND (last char was EOL or beginning)
if (ignoreEmptyLines) {
while (eol && isStartOfLine(lastChar)) {
// go on char ahead ...
lastChar = c;
c = reader.read();
eol = readEndOfLine(c);
// reached end of file without any content (empty line at the end)
if (isEndOfFile(c)) {
token.type = EOF;
// don't set token.isReady here because no content
return token;
}
}
}
// did we reach eof during the last iteration already ? EOF
if (isEndOfFile(lastChar) || !isDelimiter(lastChar) && isEndOfFile(c)) {
token.type = EOF;
// don't set token.isReady here because no content
return token;
}
if (isStartOfLine(lastChar) && isCommentStart(c)) {
final String line = reader.readLine();
if (line == null) {
token.type = EOF;
// don't set token.isReady here because no content
return token;
}
final String comment = line.trim();
token.content.append(comment);
token.type = COMMENT;
return token;
}
// important: make sure a new char gets consumed in each iteration
while (token.type == INVALID) {
// ignore whitespaces at beginning of a token
if (ignoreSurroundingSpaces) {
while (isWhitespace(c) && !eol) {
c = reader.read();
eol = readEndOfLine(c);
}
}
// ok, start of token reached: encapsulated, or token
if (isDelimiter(c)) {
// empty token return TOKEN("")
token.type = TOKEN;
} else if (eol) {
// empty token return EORECORD("")
// noop: token.content.append("");
token.type = EORECORD;
} else if (isQuoteChar(c)) {
// consume encapsulated token
parseEncapsulatedToken(token);
} else if (isEndOfFile(c)) {
// end of file return EOF()
// noop: token.content.append("");
token.type = EOF;
token.isReady = true; // there is data at EOF
} else {
// next token must be a simple token
// add removed blanks when not ignoring whitespace chars...
parseSimpleToken(token, c);
}
}
return token;
}
/**
* Parses a simple token.
*
* Simple token are tokens which are not surrounded by encapsulators. A simple token might contain escaped
* delimiters (as \, or \;). The token is finished when one of the following conditions become true:
*
* - end of line has been reached (EORECORD)
* - end of stream has been reached (EOF)
* - an unescaped delimiter has been reached (TOKEN)
*
*
* @param token
* the current token
* @param ch
* the current character
* @return the filled token
* @throws IOException
* on stream access error
*/
private Token parseSimpleToken(final Token token, int ch) throws IOException {
// Faster to use while(true)+break than while(token.type == INVALID)
while (true) {
if (readEndOfLine(ch)) {
token.type = EORECORD;
break;
} else if (isEndOfFile(ch)) {
token.type = EOF;
token.isReady = true; // There is data at EOF
break;
} else if (isDelimiter(ch)) {
token.type = TOKEN;
break;
} else if (isEscape(ch)) {
final int unescaped = readEscape();
if (unescaped == END_OF_STREAM) { // unexpected char after escape
token.content.append((char) ch).append((char) reader.getLastChar());
} else {
token.content.append((char) unescaped);
}
ch = reader.read(); // continue
} else {
token.content.append((char) ch);
ch = reader.read(); // continue
}
}
if (ignoreSurroundingSpaces) {
trimTrailingSpaces(token.content);
}
return token;
}
/**
* Parses an encapsulated token.
*
* Encapsulated tokens are surrounded by the given encapsulating-string. The encapsulator itself might be included
* in the token using a doubling syntax (as "", '') or using escaping (as in \", \'). Whitespaces before and after
* an encapsulated token are ignored. The token is finished when one of the following conditions become true:
*
* - an unescaped encapsulator has been reached, and is followed by optional whitespace then:
*
* - delimiter (TOKEN)
* - end of line (EORECORD)
*
* - end of stream has been reached (EOF)
*
* @param token
* the current token
* @return a valid token object
* @throws IOException
* on invalid state: EOF before closing encapsulator or invalid character before delimiter or EOL
*/
private Token parseEncapsulatedToken(final Token token) throws IOException {
// save current line number in case needed for IOE
final long startLineNumber = getCurrentLineNumber();
int c;
while (true) {
c = reader.read();
if (isEscape(c)) {
final int unescaped = readEscape();
if (unescaped == END_OF_STREAM) { // unexpected char after escape
token.content.append((char) c).append((char) reader.getLastChar());
} else {
token.content.append((char) unescaped);
}
} else if (isQuoteChar(c)) {
if (isQuoteChar(reader.lookAhead())) {
// double or escaped encapsulator -> add single encapsulator to token
c = reader.read();
token.content.append((char) c);
} else {
// token finish mark (encapsulator) reached: ignore whitespace till delimiter
while (true) {
c = reader.read();
if (isDelimiter(c)) {
token.type = TOKEN;
return token;
} else if (isEndOfFile(c)) {
token.type = EOF;
token.isReady = true; // There is data at EOF
return token;
} else if (readEndOfLine(c)) {
token.type = EORECORD;
return token;
} else if (!isWhitespace(c)) {
// error invalid char between token and next delimiter
throw new IOException("(line " + getCurrentLineNumber() +
") invalid char between encapsulated token and delimiter");
}
}
}
} else if (isEndOfFile(c)) {
// error condition (end of file before end of token)
throw new IOException("(startline " + startLineNumber +
") EOF reached before encapsulated token finished");
} else {
// consume character
token.content.append((char) c);
}
}
}
private char mapNullToDisabled(final Character c) {
return c == null ? DISABLED : c.charValue();
}
/**
* Returns the current line number
*
* @return the current line number
*/
long getCurrentLineNumber() {
return reader.getCurrentLineNumber();
}
/**
* Returns the current character position
*
* @return the current character position
*/
long getCharacterPosition() {
return reader.getPosition();
}
// TODO escape handling needs more work
/**
* Handle an escape sequence.
* The current character must be the escape character.
* On return, the next character is available by calling {@link ExtendedBufferedReader#getLastChar()}
* on the input stream.
*
* @return the unescaped character (as an int) or {@link Constants#END_OF_STREAM} if char following the escape is
* invalid.
* @throws IOException if there is a problem reading the stream or the end of stream is detected:
* the escape character is not allowed at end of strem
*/
int readEscape() throws IOException {
// the escape char has just been read (normally a backslash)
final int ch = reader.read();
switch (ch) {
case 'r':
return CR;
case 'n':
return LF;
case 't':
return TAB;
case 'b':
return BACKSPACE;
case 'f':
return FF;
case CR:
case LF:
case FF: // TODO is this correct?
case TAB: // TODO is this correct? Do tabs need to be escaped?
case BACKSPACE: // TODO is this correct?
return ch;
case END_OF_STREAM:
throw new IOException("EOF whilst processing escape sequence");
default:
// Now check for meta-characters
if (isMetaChar(ch)) {
return ch;
}
// indicate unexpected char - available from in.getLastChar()
return END_OF_STREAM;
}
}
void trimTrailingSpaces(final StringBuilder buffer) {
int length = buffer.length();
while (length > 0 && Character.isWhitespace(buffer.charAt(length - 1))) {
length = length - 1;
}
if (length != buffer.length()) {
buffer.setLength(length);
}
}
/**
* Greedily accepts \n, \r and \r\n This checker consumes silently the second control-character...
*
* @return true if the given or next character is a line-terminator
*/
boolean readEndOfLine(int ch) throws IOException {
// check if we have \r\n...
if (ch == CR && reader.lookAhead() == LF) {
// note: does not change ch outside of this method!
ch = reader.read();
}
return ch == LF || ch == CR;
}
boolean isClosed() {
return reader.isClosed();
}
/**
* @return true if the given char is a whitespace character
*/
boolean isWhitespace(final int ch) {
return !isDelimiter(ch) && Character.isWhitespace((char) ch);
}
/**
* Checks if the current character represents the start of a line: a CR, LF or is at the start of the file.
*
* @param ch the character to check
* @return true if the character is at the start of a line.
*/
boolean isStartOfLine(final int ch) {
return ch == LF || ch == CR || ch == UNDEFINED;
}
/**
* @return true if the given character indicates end of file
*/
boolean isEndOfFile(final int ch) {
return ch == END_OF_STREAM;
}
boolean isDelimiter(final int ch) {
return ch == delimiter;
}
boolean isEscape(final int ch) {
return ch == escape;
}
boolean isQuoteChar(final int ch) {
return ch == quoteChar;
}
boolean isCommentStart(final int ch) {
return ch == commentStart;
}
private boolean isMetaChar(final int ch) {
return ch == delimiter ||
ch == escape ||
ch == quoteChar ||
ch == commentStart;
}
/**
* Closes resources.
*
* @throws IOException
* If an I/O error occurs
*/
@Override
public void close() throws IOException {
reader.close();
}
}